1. Field of the Invention
The present invention relates to a fluorescent lamp in which a discharge path is formed by connecting a plurality of glass tubes with each other.
2. Related Background Art
Conventionally, fluorescent lamps, each having a discharge path that is formed with a plurality of glass tubes connected with each other, have been known widely as so-called compact fluorescent lamps, bulb-formed fluorescent lamps, and double ring-shaped fluorescent lamps. As to a type of connection of glass tubes, a bridge connection type and a mold-connection type commonly are used for the foregoing lamps.
In the bridge connection-type fluorescent lamp, a stress is applied in such a direction to shrink a gap between connected glass tubes when the lamp is mounted to a lighting equipment. Configurations in each of which spacers are provided in a gap between glass tubes to increase the strength of the lamp against the stress are disclosed by, for instance, JP62-264547A, and JP05-76132B. In the case where accuracy of the gap between the glass tubes is high, such spacers placed in the gap are effective in reinforcing the strength of the lamp. Another configuration in which spacers, each composed of two pieces that fit each other so as to be prevented from dropping off, are set in the gap between sides of the glass tubes is disclosed by JP03-254059A.
In the case where the gap accuracy between the connected glass tubes is insufficient, a spacer tends to drop off at a position where the gap is wide. This drawback is particularly likely to occur in the double ring-shaped fluorescent lamp of the bridge connection type. Furthermore, in the case where the spacer composed of two pieces that fit each other is used, there is a drawback in that it is difficult to efficiently carry out the work of fitting the spacer in a gap between glass tubes.
Therefore, to solve the foregoing problems, it is an object of the present invention to provide a fluorescent lamp in which spacers are prevented from dropping off even with insufficient gap accuracy of glass tubes, and to which spacers are attached readily.
To achieve the foregoing object, a fluorescent lamp according to the present invention has a plurality of glass tubes that are connected with each other to form a discharge path, and a spacer that is provided in a gap between the glass tubes. In the fluorescent lamp, the spacer is composed of a plurality of tonguelets and a bridge, and the tonguelets are in contact with surfaces of the glass tubes and are connected by the bridge directed in an axial direction of the glass tubes.
According to this, a plurality of tonguelets are disposed in the gap between the glass tubes at a plurality of positions along the axial direction of the glass tubes, respectively. Therefore, it is possible to provide a fluorescent lamp with a high gap compression resistance and a high torsion resistance, in which the spacers hardly drop off even in the case where the width of the gap between the glass tubes varies.
Furthermore, in the foregoing fluorescent lamp, the spacer preferably is formed by connecting two tonguelets via the bridge.
Furthermore, in the foregoing fluorescent lamp, the glass tubes preferably are non-linear. In this configuration, the gap between the glass tubes is curved, thereby exerting a force to bend the bridge of the spacer. This generates a stress applied to the two tonguelets in the opposite direction of the stress caused in the bridge, thereby increasing the spacer grasping force. Consequently, even in the case where the gap between the glass tubes varies greatly, the spacers inserted at a position where the gap is wide are prevented from dropping off.
Furthermore, in the fluorescent lamp of the present invention, the glass tubes preferably are formed in a double ring shape. With this configuration, it is possible to provide a double ring-shaped fluorescent lamp with a high gap compression resistance and a high torsion resistance even in the case where the accuracy of the width of the gap is insufficient.
Furthermore, in the fluorescent lamp of the present invention, a distance between central lines of two adjacent tonguelets of the spacer preferably is in a range of {fraction (1/10)} to xc2xd of a distance from a central point of the double ring to the gap in the double ring. Therefore, the stress exerted to the two tonguelets in opposite directions is never too small, thereby by no means causing the spacers to drop off. Also the stress is never too great, thereby by no means degrading the strength of the bridge portions of the spacers or the strength of the glass tubes. Thus, generally a sufficient spacer grasping and holding force can be secured.
Furthermore, in the foregoing fluorescent lamp, it is also preferable that the glass tubes are linear. In this configuration also, a plurality of tonguelets are disposed in the gap between the glass tubes at a plurality of positions along the axial direction of the glass tubes, respectively. Therefore, it is possible to provide a fluorescent lamp with a high gap compression resistance and a high torsion resistance, in which the spacers hardly drop off even in the case where the width of the gap between the glass tubes varies.
Furthermore, in the fluorescent lamp of the present invention, at least a portion of each of the spacers has elasticity. In this configuration, the spacers can be attached extremely easily only by pressing and fitting the spacers in the gap between the glass tubes.
Furthermore, in the fluorescent lamp of the present invention, the spacers preferably contain a transparent resin. This allows the lamp to light uniformly. As the transparent resin, polycarbonate or the like may be used. The use of polycarbonate allows the stress exerted to the tonguelets for supporting use to be maintained uniformly even with respect to thermal changes while the lamp is turned on.